Searching for NI's shipwrecks and planes lost at sea

Colin Dunlop is not your typical civil servant.
On the day we join him, his commute is not by car or bus, his working environment is not a hot-desking city centre office and what he's searching for does not, for the most part, come via email or spreadsheet.
Instead, his nine-to-five is on the sea, where his job is to find, map and help protect Northern Ireland's hidden marine heritage. That includes hundreds of sunken ships and crashed planes that litter the seabed off the coast.
That's why we're here, bobbing about off the coast of Rathlin Island, about 30 minutes sailing from Ballycastle.